Serious safety issue! -Master cylinder mods (2 Viewers)

[Pin_Head]

The pads don't really retract. It is just the run out of the disk and the Bernouli effect of the air flow that moves them a tiny bit.

The valves in the US and NZ masters look different in the pictures posted, so maybe they work differently. I don't know that they are different, but brakes are one of the many issues for importing "grey market" (non-US spec) vehicles into the US.

 

[Plowboy]

Hi Charley,
My 40 has been up on blocks for about six months in Idaho. A couple of weeks aog I was working on putting a locker in the front end. Because of a busted soft line there hasn't been any fluid in the front.
When I pulled the calipers, no need to spread the pistons, they were all the way back to the new pad location. With out the retainers the pads would have fallen out.

 

[pbgbottle]

I love this thread lostmarbles .these valves have had me thinking about them on more than one occasion . i posted it in the other thread but we do have the same valves here in our 4 wheel DRUM brake masters (U.S./CAN) . the plastic ones are in our front DISC brake masters


edit this was refering to PIN_HEAD'S post

 

[lostmarbles]

he concludes, it is more dangerous to have a MC without valves .

Thanks for trying to clarify what I am trying to say Mr. Toad. (I think saying the same thing a different way always helps.)

The only thing I would like to add to your summary is that it has become apparent to me from all this that SOME mastercylinders on SOME vehicles do indeed have "true residual pressure valves" that do indeed leave residual pressure in the brake lines. (I have yet to conclude whether or not they were ever fitted to any 40 series cruisers though.)

I am unsure whether removing one of these "true residual pressure valves" would represent a safety issue.

Can someone show a close-up photo of one of those white plastic valves? Preferably showing an unvalved (permanently-open) flow-hole (if one exists) that would prove they don't/can't leave residual pressure. (Perhaps the numbers on them aren't pressure ratings at all??)

It makes sense to me that you need "true residual pressure valves" when a mastercylinder is located below the wheel cylinders -- To stop the tendency for fluid to drain backwards into the reservoir(perhaps sucking-in the cylinder pistons at the same time).

....... Further thought.......... Perhaps I've got it now? .......When you take your foot off the brake and the pistons inside the mastercylinder move back, any suction produced by this movement should be mostly eliminated by fluid-return from the wheel cylinders. But some suction could remain. This suction would normally cause fresh fluid to enter the chamber from the reservoir (around the seal set-up designed for this "topping-up process"). So design engineers may want to install "true residual pressure valves" to stop the possibility of this suction actually pulling-in wheel pistons (on a disc system) or of the possibility of it sucking in air through a leaky wheel cylinder (any type of system). Does this make sense?

 

[lostmarbles]

"There are "spring clips" but they just encourage the pistons to go back a millimetre or two at most."

Yes there are spring clips that do just that, except as the pad wears down those clips will encourage the piston to go back to the non worn position, increasing the gap between the disk and pad. and the brake pedal gets lower and lower, till you feel a need to pump the brakes

OOops. I used the wrong words I think. I meant those bits of spring-sheetmetal that tend to sit directly behind the pads. Often they have a "pressing" in them that gives them a little bit of "spring".
Second thoughts - Forget I ever placed that post.

I agree with you. (but those springs you refer to are so weak I doubt they achieve much.) (One or the other of these things is there for anti-rattle purposes I seem to remember too.)

 

[lostmarbles]

"grey market" (non-US spec).

The "grey market" is non-NZ spec. You're perspective is wrong Pin_Head.

 

[nuclearlemon]

he concludes, it is more dangerous to have a MC without valves because you'll have to pump more in the emergency situation that all of us hope never to encounter. It makes sense.

Personally, I removed the valve when I did my FDB conversion years ago. We've all been conditioned to do this because it's part of Cruiser Modification Lore. Everything has been fine, but then I've never been in an emergency situation with failing hydraulics. So I'll monitor the system, fluid levels, etc. a little more carefully now. And next time I do a complete fluid change, I'll look for a replacement valve to re-install.

but do you ever have to pump your pedal on just a hard stop? if you don't have to pump it then, you won't have to pump it in a panic stop.

with no valves front or rear (i'm 4w disc), i've never had a soft pedal feel.

 

[Mace]

but do you ever have to pump your pedal on just a hard stop? if you don't have to pump it then, you won't have to pump it in a panic stop.

with no valves front or rear (i'm 4w disc), i've never had a soft pedal feel.

Ige, he is talking about needing to pump the brakes when your brakes are not working correctly..

 

[lostmarbles]

Ige, he is talking about needing to pump the brakes when your brakes are not working correctly..

I admit I can't follow what is being said either.

Here's another go at my side of the story:

My braking system, if properly bled and adjusted, would still achieve "a hard pedal" during braking (and have "freeplay", "pedal height" and whatever-else perfectly "within spec") if I was to throw away my "valve thingies". In other words, no normal brake inspection/test would reveal any harm done.

But if I was careering along without the "thingies" and with serious air contamination of my hydraulic fluid, I would be MUCH less likely to ever be able to slow my vehicle down before crashing.

 

[Pin_Head]

Hi Charley,
My 40 has been up on blocks for about six months in Idaho. A couple of weeks aog I was working on putting a locker in the front end. Because of a busted soft line there hasn't been any fluid in the front.
When I pulled the calipers, no need to spread the pistons, they were all the way back to the new pad location. With out the retainers the pads would have fallen out.

Larry,
Bummer. I don't get to drive mine either because my son wants to drive it now and he is bigger than I am.

The "grey market" is non-NZ spec. You're perspective is wrong Pin_Head.

It depends on your point of reference, just like sheep jokes.

"A Kiwi and a Pommy are walking through a paddock, when straight away, the Kiwi spots the best looking ewe in the flock."

You can fill in the blanks.

 

[grant5127]

It depends on your point of reference, just like sheep jokes.

"A Kiwi and a Pommy are walking through a paddock, when straight away, the Kiwi spots the best looking ewe in the flock."

You can fill in the blanks.

LOL! ......

 

[lostmarbles]

LOL! ......

Hey. I'll have to seek out that thread!!!! Then I'll be able to tally up all my foes!

Now lets see. Crushers, now Pin_Head too, and ...........

Oops THAT thread was THIS thread. Doh!

Well. We're supposedly outnumbered by sheep. So that's just natural "species evolvement" where our environment has been tampered with ----or perhaps its just our version of "genetic engineering"

 

[Pin_Head]

Well. We're supposedly outnumbered by sheep.

Well, if your are familiar with that genre of joke, regardless if you are a Kiwi or you are from OZ, the joke is always on the Pommy.

On a more serious safety issue, since the All Black lost to the French, has the suicide rate gone up?

 

[lostmarbles]

Well, if your are familiar with that genre of joke, regardless if you are a Kiwi or you are from OZ, the joke is always on the Pommy.

On a more serious safety issue, since the All Black lost to the French, has the suicide rate gone up?

No way of telling. Our Press won't publish figures because it encourages copycat activity.

But I do know that many owners of BMW cars are finding their roofs stoved in.

 

[jwest]

I don't think that the removal of these valves from a drum brake master for a FDB modification poses any more of a safety hazard than installing a 2lb valve in it's place for this reason: Land Cruisers, by nature and design, have their master cylinders situated well above the calipers. As such, and until the laws of nature on our planet change, gravity will allow for a constant amount of residual pressure, enough to keep the pads from fully retracting.

.

 

[lostmarbles]

gravity will allow for a constant amount of residual pressure, enough to keep the pads from fully retracting.

Yes. I was thinking the same thing about the height jwest. Not many vehicles would achieve a bigger height difference (than our 40 series) between the reservoir fluid level and the cylinder levels. And such a "head of fluid" would indeed provide "residual pressure" on its own. (Probably considerably less than 2psi though but still measurable.)


But I don't understand how any "residual pressure" improves how a mastercylinder copes with the effects of air-contamination.

It was by looking at the design of those "caps" that I discovered their ability to "favour outwards fluid flow". (5 paths compared to only 1)

Hey- Just thought of something that COMPLETELY TORPEDOS MY ARGUMENT THUS FAR ABOUT THE SAFETY ASPECT (Do many others try and torpedo their own arguments?)

WHAT IF A "CAP" WERE TO LIFT OFF ITS SEAT DURING THE "BACK-FLOW PHASE" (WHEN YOU'RE LIFTING YOUR FOOT OFF THE BRAKE PEDAL). THEN THE BACK-FLOW WOULD ACTUALLY BE MASSIVELY HIGHER THAN ANY POSSIBLE OUT-FLOW !!! (Up till now I've been assuming they wouldn't lift but how can I judge that?)

Relax everyone about reinstalling their thingies!!!! (If you took any notice of me in the first place. I am LostMarbles after-all.)

What we need is a "brake expert" to read all this and give their view on what job my "valve thingies" are actually installed to do. I still maintain my stand that they don't/can't maintain residual pressure.

But the strong opinion I held that they helped in dealing with aircontamination is now severely weakened.

 

[Pin_Head]

But I don't understand how any "residual pressure" improves how a mastercylinder copes with the effects of air-contamination.

But the strong opinion I held that they helped in dealing with aircontamination is now severely weakened.

That is an easy one. They don't help cope with the effects of air. Air is bad and abnormal under any circumstance. That is why you bleed brakes.

What we need is a "brake expert" to read all this and give their view on what job my "valve thingies" are actually installed to do. I still maintain my stand that they don't/can't maintain residual pressure.

The valve thingys in NZ M/Cs only bias flow rate. Most of the valves in the US M/Cs actually maintain residual pressure. If you google the term, you can find several explanations for them; all of which sound reasonable. The reason for the different types of valves may be to make it harder to import and export vehicles into and out of the US.

 

[Mace]

= You are overreacting

 

[lostmarbles]

They don't help cope with the effects of air.

Well so far no-one has successfully explained to me what they do Pinhead. (But I admit I'm not the sharpest knife in the draw.)

If I don't know why the Toyota brake engineer fitted them, then surely I can't rule out that they are there for some safety purpose. (I'm just no longer sure that their purpose relates to safety and/or air-contamination.)

Mine have been reinstalled and I wouldn't consider discarding them unless I understood the consequences of doing that.

The valve thingys in NZ M/Cs

You're ignoring pbgbottle's contribution to this post Pin_Head. He tells us it is not just a "New Zealand thing". The same valve thingies are fitted to vehicles originally sent to your country.

The valve thingys in NZ M/Cs only bias flow rate.

Now we are getting somewhere. Just tell me the purpose this is meant to achieve (and remember that front and rear valves are IDENTICAL) and you may actually get through to me!!!!!!! (Please Please Please. I'm begging!!!!!!)

Most of the valves in the US M/Cs actually maintain residual pressure.

Not sure if you're right or wrong here. (You're wrong if the majority of the valves are the same as mine.) Only others from your country could answer this.

If you google the term, you can find several explanations

Do you mean the term "residual valve" Pin_Head? Gosh - I've read so much stuff about them that I'm getting a headache.

Can you answer me this question. How can my "valve thingies" maintaintain "residual pressure" when each of them has a through-hole that allows pressures to equalise under all conditions? Only if you can answer this, will I accept that what I have are "residual valves".

 

[lostmarbles]

Summary of my position

:whoops:
Now that I have found flaws in my safety/air-contamination argument, I feel like a dickhead for jumping in and raising concerns about the practice of discarding the brake cylinder "outlet valves".

Most people label my "outlet valves" as "residual valves" But I maintain that my "outlet valves" don't/can't leave "residual pressure". So they shouldn't be called "residual valves". Furthermore, no-one has yet clearly explained to me their real purpose.

Without being sure of what they do - I still think it would be dangerous to discard them.